Plumbing breather to airbox or catch can, what is best?

[Riceburner]

I looking at getting an airbox to suit my oddball setup. I was wondering if it is possible to race with the breathers plumbed into the airbox as per the factory setup or is a catch can definately a requirement?

 

Will the PCV&crankcase venting into the airbox have any effect on tuning/power? The airbox will be ducted into the front of my G-nose.

 

Thanks, Gareth.

[PZG302]

Gareth,

 

plumb it into the catch can, that's where you want to catch the oil. The breathers are only plumbed into the airbox for emissions.

 

And with the catch can make sure it's up around 2 litre capacity, it may have to be more depending on what events you are doing, best to check teh CAMS manual on line.

[Riceburner]

I think Cams state it need to be engine capacity, I currently have a 2ltr one hooked up. As it is still street driven occasionally I was thinking of running them into the airbox to be a bit more EPA/COP friendly, then on race days connect them to the catch can and cap off the airbox fittings.

 

Or is it possible to run both the CC&PCV breathers into a catch can and the instead of running a filter on top of the catch can run a line back to the air box into PCV valve?

 

 

[PZG302]

You could do that, but with the age of the car and if you make it look neat I can't see a problem with not venting into the air box.

 

IIRC ADR's for pollution didn't come in until 1974.

[nizm0zed]

Definately into the catch can.

Fill your catch can with steel wool to filter the oil from the air.

Depending on the design of the can (inlet and outlet) you may need a baffle plate so that the air does go through the filter instead of just over the top.

To keep it EPA friendly you should then vent the catch can into your inlet, after the air filter but before the throttle.

If you really want to screw every last killerwasp out of your engine, use a vacuum scavenge pump to keep your crankcase at vacuum, then output that through the catch can.

You'd have to want to spend a lot of money for a little gain though 

[Riceburner]

Thanks guys

[Six_Shooter]

Have you removed the baffle from the cam cover?

 

On all of my street vehicles, I have NEVER used a catch can, they are pointless, when using a baffled cam/rocker cover.

 

The only reason that "catch cans" were ever used before people started convincing themselves they are building race cars for the street was with engines that didn't use a baffled cam/rocker cover.

 

I have never had any excess oil in the intake tract, in fact most are usually bone dry. because I set up my PCV systems correctly, with the other end being connected to the intake plenum, using a proper PCV, in boosted applications, one that actually closes off when positive pressure is applied to the plenum side. In boosted applications, I route the breather to the inlet to the turbo. I usually also add a angle cut to the tube to apply vaccum when the turbo is spinning at high speed, where the PCV will be closed.

 

That being said, if it's a requirement of a racing body that you are running in, then follow their rules, otherwise, catch cans on street cars is pointless, with baffled cam/rocker covers.

[260Coupe]

I couldn't agree more.........venting crank case gas to the atmosphere is the first thing the EPA/constabulary check for (I know from experience) and there is little/no measurable gain on the dyno for venting to a catch can rather than re-burning the gases.

 

If you are installing an air box then plumb in the rocker cover and crank case vent.

 

my 2c

 

Al.

[Riceburner]

Some very helpful here, if i can manage to fit an air box in it will be plumbed to the catch can and back to the air box. thanks guys

[d3c0y]

What if you run triples with no airbox. What are you supposed to do with it then?

[nizm0zed]

one way valve into the inlet runners so the vacuum of the engine sucks the vapours in?

[NZeder]

Not sure CAMS rules are the same as some of ours here in NZ but as of Jan 2013 new builds must not have the catch can on the same side as the exhaust (if possible ie V6/V8/V12 etc that might not be possible) but inline engines that is the case.

[d3c0y]

one way valve into the inlet runners so the vacuum of the engine sucks the vapours in?

 

 

That would create a fair bit of vacuum comparable to the brake booster. OEM setups always go into the airbox which wouldn't have anywhere near that level.